There are a number of techniques for measuring voltages on a flat panel display which comply with the requirement that there be no electrical contact on the active area of the flat panel display to avoid contamination of the electrode surfaces although the electrical contact may be made at the edges of the flat panel display. For example, an electron beam may be used to image the surface with voltage differences appearing as contrast differences. However, testing of the thin film circuitry for Organic Light Emitting Diode (OLED) flat panel requires measuring the current because the OLED pixel brightness is controlled using a current signal as opposed to a voltage signal used to control brightness for Liquid Crystal Display (LCD) pixel
Typically, it is more difficult to measure currents. One typical technique is to incorporate an additional capacitor per pixel on the OLED display circuit and to measure the charging of this capacitor. This technique typically adds complexity to the circuit that will not be used once testing is complete. Another typical technique uses an electron beam as a non-contact probe but this technique requires placing the flat panel under test into a vacuum chamber which adds cost and time to the test procedure.